Dispensing devices

ABSTRACT

An electrostatic spraying device comprising a nozzle, means for establishing a column of material to be sprayed within a passage leading to the nozzle outlet such that the leading surface of the column is spaced from the nozzle outlet, means for pneumatically ejecting said column or part thereof from the nozzle and means for applying high voltage to the material so that the spray formed by breaking up of the column on ejection from the nozzle are electrically charged. The column of material in the passage is preferably a discreet slug having a leading surface spaced from the nozzle outlet and a trailing surface to which air, gas or vapor under pressure can be applied to effect ejection of the slug from the nozzle.

This invention relates to dispensing devices.

The invention has particular application to electrostatic sprayingdevices for use in applications involving for example air freshening,air purification, insecticide spraying, personal care/hygiene products(e.g. deodorants, cosmetics and perfumes) and medical and quasi-medicalproducts such as nasal and respiratory tract sprays.

The present invention seeks to provide a device which is capable ofefficiently delivering material in small amounts and/or in a relativelyshort duration of time.

EP-A-224352 discloses an electrostatic spraying device for dispensingopthalmically active compounds in discrete measured quantities. In thedisclosed device, liquid is supplied to the tip of the nozzle and apotential difference is applied between the nozzle and an electrodespaced from the nozzle so that an electrical field of sufficientstrength is provided at the outlet of the nozzle to draw the formulationaway from the outlet as one or more ligaments which then break up intodroplets. To enable the liquid to be drawn into ligaments, the liquidmust be present at the very tip of the nozzle at the time of applicationof the potential difference. Liquid feed is supplied to the nozzleeither from a reservoir of liquid within the device or by drawing theliquid from a separate source using a pipette action.

According to one aspect of the present invention there is provided anelectrostatic spraying device comprising a nozzle, means forestablishing a column of material to be sprayed within a passage leadingto the nozzle outlet such that the leading surface of the column isspaced from the nozzle outlet, means for pneumatically ejecting saidcolumn or part thereof from the nozzle and means for applying highvoltage to the material so that the spray formed by breaking up of thecolumn on ejection from the nozzle are electrically charged.

According to a second aspect of the invention there is provided a methodof electrostatic spraying comprising establishing a column of materialto be sprayed within a passage leading to the outlet of a sprayingnozzle of the device such that the leading surface of the column isspaced from the nozzle outlet, pneumatically ejecting the column ofmaterial or part thereof from the nozzle and applying high voltage tothe material so that the spray particles formed by breaking up of thecolumn on ejection from the nozzle are electrically charged.

Preferably the column of material is established in the passage as adiscrete slug having a leading surface spaced from the nozzle outlet anda trailing surface to which air, gas or vapour under pressure can beapplied to effect ejection of the slug from the nozzle.

According to a further aspect of the present invention there is providedan electrostatic spraying device comprising a nozzle, means forestablishing a discrete slug of material to be sprayed within a passageleading to the nozzle outlet (preferably in such a way that the leadingsurface of the slug is spaced from the nozzle outlet), means forpneumatically ejecting said slug from the nozzle and means for applyinghigh voltage to the material so that the spray particles formed bybreaking up of the column on ejection from the nozzle are electricallycharged.

Usually the material will comprise a single phase liquid formulation;however, we do not exclude application of the invention to materials inthe form of liquid containing suspended solids. The formulation forinstance may comprise more than one liquid in admixture—for example, theformulation may comprise an active ingredient such as a nasaldecongestant agent, a diluent and other agents such as viscosity and/orresistivity modifying agents. Also we do not exclude the possibility ofthe material being in the form of pneumatically transportable fluentmaterial other than a liquid, e.g. a powder.

In the device according to said one aspect of the present invention acolumn, preferably in the form of a discrete slug, of the material to besprayed is established within the passage so that the column/slug islocated with its leading surface (meniscus) spaced from the nozzleoutlet. This allows the column/slug to be cleanly ejected from thenozzle outlet since the column/slug undergoes acceleration as it travelstowards the nozzle tip and a relatively high velocity can therefore beimparted to the liquid before it reaches the nozzle tip. If for examplea liquid is located with its leading meniscus at the nozzle tip prior tobeing displaced pneumatically, the liquid will have a low velocity atthe beginning of the spraying operation and, in these circumstances, wehave found that there is a tendency for spray attachment to the nozzleto occur at the beginning of the spraying action. Likewise, because thepreferred method and device isolate a slug of the liquid within thepassage leading to the nozzle outlet, the slug has a trailing surfaceand can exit cleanly from the nozzle without any significant tendencyfor spray attachment to occur, as would be the case for instance wherethe liquid in the passage is a continuation of, rather than beingisolated from, the body of liquid from which it is derived.

Preferably the high voltage is applied to the material at or near to thenozzle outlet.

According to a narrower aspect of the invention there is provided anelectrostatic spraying device comprising a nozzle, means forestablishing a column of liquid within a passage leading to the outletof the nozzle such that the leading surface of the slug is locatedupstream of a reduced cross-section portion leading to the nozzleoutlet, means for pneumatically ejecting the slug as a jet from thenozzle and means for applying high voltage to the slug so that thedroplets of the spray formed by breaking up of the jet are electricallycharged.

Although not limited to any particular range of resistivity, theinvention has particular application to low resistivity materials,especially liquids; e.g. liquids having a bulk resistivity of less thanabout 1×10⁷ ohm cm including liquids having a resistivity significantlyless than 1×10⁴ ohm cm, e.g. 1×10³ ohm cm and lower.

Preferably the arrangement is such that the jet of material at the pointof egress from the nozzle has a diameter no greater than 300 micron andusually no less than about 15 micron. For example, the diameter of thejet at the point of egress may be in the range from about 20 to about150 micron, more preferably 25 to 125 micron and most preferably 30 to80 micron.

The nozzle design is preferably such that the surface of the nozzle atthe point of egress of the material to be sprayed is not prone to createcorona discharge. Thus as disclosed in prior EP-A-510725, bluff-endednozzles are therefore preferred when the material to be sprayed has lowresistivity.

The fluid pressure generated to effect pneumatic ejection of the slug isconveniently produced in response to operation of actuating means by theuser and such operation of the actuating means may also be accompaniedby priming of the passage leading to the nozzle outlet with thecolumn/slug in preparation for pneumatic ejection. The priming actionand fluid compression may occur substantially simultaneously and thearrangement may be such that operation of the actuating means is alsoaccompanied by operation of a high voltage generator associated with themeans for applying high voltage to the material to be sprayed wherebyall of these operations together with ejection of the column/slug areeffected in response to a single operation of the actuating means by theuser. For example, the actuating means may normally be in a standbystate and the arrangement may be such that operation of the actuatingmeans is initially accompanied by compression of fluid and priming ofthe passage leading to the nozzle with the slug/column, followed bycommunication of the compressed fluid with the interior of the passageand by operation of the high voltage applying means so that, as the slugis displaced by the fluid pressure, the slug traverses a contact regionat or in the immediate vicinity of the nozzle outlet where the highvoltage is applied to the slug.

Instead of all operations being effected in response to a singleoperation on the part of the user, they may instead be decoupled. Forexample, at least priming of said passage with the slug/column may takeplace in response to operation of a first actuator, and the compressionof the fluid (where necessary), application of high voltage andcommunication between the compressed fluid and the slug/column may takeplace in response to operation of a second actuator. Where the fluidused for ejection of the liquid is not pre-compressed but has to becompressed in the course of using the device, such compression may beeffected in response to operation of the first actuator or the secondactuator. Decoupled operation of the device in this way may be desirablewhere it is more convenient for the user to prime the device initiallyin preparation for use without necessarily having to locate the nozzlein any specific position before priming is effected, for instance as isrequired where the device functions as a nasal decongestant spray.

In one embodiment of the invention, the actuating means may bedisplaceable from a standby condition by the user and may be biassed tothe standby condition, e.g. by spring loading, so that the actuatingmeans automatically restores to the standby position following actuationby the user. Thus, for instance, user-effected displacement of theactuator from its standby condition may be accompanied by said fluidcompression (and optionally by priming of said passage) and automaticreturn of the actuator may be accompanied by pneumatic ejection of, andapplication of high voltage to, the column or slug. Alternatively,user-effected displacement of the actuator in one direction from itsstandby condition may be accompanied by said fluid compression, ejectionof the column or slug and application of the high voltage to the slug.The return stroke of the actuator may restore the device in preparationfor the next dispensing operation and may for example be accompanied bydisabling of the voltage supply and priming of the passage with a freshslug/column.

Typically the pneumatic ejection will involve delivery of up to about100 μl of the material from the nozzle. Usually the amount delivered oneach operation will be a substantially constant volume in the range fromabout 2 to about 50 μl.

The material from which the nozzle is fabricated is desirably one towhich the material to be sprayed is not prone to adhere, especially overthat region of said passage which is occupied by the material prior topneumatic ejection. In the case where the liquid to be sprayed is aliquid or liquid-based formulation, the nozzle is desirably fabricatedat least in part from a hydrophobic material which has low wettingcharacteristics, such as PTFE. Alternatively the nozzle may be providedwith a hydrophobic coating in said region and/or on its external surfacearound the nozzle outlet so as to suppress liquid “creep” and wetting.The coating may for instance be of an organo-silicon compound.

Preferably the tip region of the nozzle is of reduced diameter relativeto that section of the nozzle upstream of the tip region. The diameterof the passage leading to the nozzle outlet will usually be sufficientlyfine that any tendency for the pressurised fluid to by-pass the columnor slug is avoided.

The device may be portable as a unit, i.e. the device may comprise ahousing incorporating a high voltage generator, a reservoir forcontaining the material to be sprayed, the nozzle tube with means fortransferring a column or slug of the material into the nozzle tube andmeans for pneumatically ejecting the column or slug of material from thenozzle outlet. In some applications, the device may be suitable forhandheld use, preferably in such a way that operation of the device canbe effected by manipulation of the device using the hand in which thedevice is held. Such manipulation may for example involve use of one ofthe fingers or the thumb to operate one or more actuators of the device.

In other applications of the invention, the device may be portable as aunit but may be designed for location on a support surface—for instance,the device may be used for dispensing formulations suitable for roomfragrancing and/or air purification in which case it may be designed forplacement on a horizontal surface such as a window sill or shelf or formounting on a vertical surface such as a wall.

In some instances, the device may not be portable as such but may bedesigned as a fixed unit for instance in the coating of articles orapplying marking agents thereto. In this event, operation of the devicemay be initiated automatically by means of a sensor arranged to sensethe presence of for instance the article at the location at which thecoating or other formulation is to be applied to the article.

In each case mentioned above. i.e. portable, handheld and fixed devices,the operation of the device is conveniently initiated in response toactuation of a single or more than one actuator or sensor and thearrangement is such that actuation leads to initiation of the followingsteps:

transfer of the material to be sprayed into said passage;

pneumatic ejection of the column/slug; and

application of the high voltage to the column/slug in the course ofejection.

The high voltage may be unipolar or it may be bipolar as disclosed inour prior EP-A-468735 and EP-A-468736, the entire disclosures of whichare incorporated herein by this reference. Thus, the bipolar voltage maybe employed to secure a measure of shock suppression and/or tofacilitate the spraying of insulating targets (e.g. as in the case of ahair spray) as disclosed in EP-A-468735 and EP-A-468736. Where a bipolarsource of voltage is employed, the arrangement is preferably such thatsuccessive slugs (or successive groups of slugs) of material dischargedfrom the nozzle are charged with voltage of opposite polarity. Thus,means may be provided for coordinating the application of the voltage tothe material being discharged with pneumatic ejection in such a way thatsuccessive slugs of the material (or successive groups of slugs) arecharged with voltage of opposite polarity. This is particularly the casewhere each operation of the device results in the ejection of multipleslugs of material rather than just a single slug per operation of thedevice.

In the various aspects of the invention as defined above, preferably thearrangement is such that the voltage is applied to each slug of materialonly after the slug has been physically isolated from the reservoir ofmaterial within the device.

According to a further aspect of the present invention there is providedan electrostatic spraying device comprising a nozzle, a reservoir forcontaining material which is to be sprayed, a passage connecting thereservoir to the nozzle, means for establishing a column of saidmaterial to be sprayed within the passage such that the trailing surfaceof the column is separated from the remainder of the material in thereservoir whereby the gap affords electrical insulation between the tipof the nozzle and the reservoir, and means for applying high voltage tothe column of material so that the spray particles formed by breaking upof the column on ejection from the nozzle are electrically charged.

In this manner, it is possible to secure electrical isolation of thematerial in the reservoir from the column or slug of material to whichthe high voltage is applied. This, in turn, permits the reservoir to beearthed if desired and the part of the device housing the reservoir maybe held in the hand without necessarily having to insulate the user fromthe material in the reservoir. Such electrical isolation of the mainbody of material to be sprayed from the column or slug to which voltageis applied may be particularly advantageous since the capacitance of thedevice during spraying can be reduced significantly and more rapidbuild-up of the electric field is possible on application of the highvoltage since the voltage is applied to a much smaller quantity of thematerial to be sprayed. Where the voltage is bipolar, the main body ofthe material stored in the device is not subject to the voltage swingsthat occur and because the slug of material can be ejected cleanly fromthe nozzle, there is a reduced tendency for spitting to occur.

Thus far, the invention has been defined in terms of producing a sprayin which the spray particles are electrically charged by the applicationof high voltage. However, we do not exclude the possibility ofeliminating the high voltage source. In this aspect of the inventionthere is provided a spraying device comprising a nozzle, a reservoir forcontaining material which is to be sprayed from the nozzle, means forpriming a passage leading to the nozzle with material from the main bodyof material in the reservoir, and means for pneumatically ejecting thematerial so primed from the nozzle.

In this aspect of the invention, the material to be sprayed may forexample comprise a liquid formulation in which case the liquid forms aspray as a result of hydraulic break-up. Where the material comprises apowder, the spray may form as a result of the powder becoming dispersedfollowing ejection from the nozzle.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a schematic view of a nozzle for use in the present invention;

FIG. 2 is a view similar to that of FIG. 1 with the slug or column ofliquid to be sprayed shown partly ejected from the nozzle;

FIG. 3 is a schematic view showing an embodiment of the invention foruse in the delivery of nasal decongestant or like formulations;

FIG. 4 is a schematic view of another embodiment in which the sequenceof operation is effected by means of a single actuator; and

FIGS. 5 and 6 are views similar to those of FIGS. 1 and 2 but showing amodified method of liquid discharge.

At FIG. 1 illustrates the principle of operation of devices inaccordance with the present invention. The device comprises a nozzletube 10 terminating in a tip 12 at one end which forms an outlet fromwhich the liquid to be sprayed is dispensed in use. The liquid to besprayed is established within the nozzle tube 10 as a column or slug 14in such a way that the leading surface of the column 14 is spaced fromthe tip 12 of the nozzle. In this manner, a pocket of air is presentbetween the leading surface of the column 14 and the nozzle tip. Inaddition, prior to or during the course of ejecting the column 14 fromthe nozzle tube 10, a pocket of air (or other gas or vapour) isestablished at the trailing surface of the column 14. The column 14 isexpelled from the nozzle tube 10 by means of a pressurised gas or vapourapplied to the trailing surface of the column 14 (see arrow P). Thediameter of the tube 10 is sufficiently small that the pressurised gasor vapour cannot by-pass the column 14.

High voltage, e.g. typically of the order of 1 to 8 kV (but dependent onthe particular application of the device) is applied to the nozzle tubeby voltage generator (not shown). For this purpose the tube 10 includesa section 16 which is sufficiently electrically conductive for thedesigned purpose of applying high voltage to the liquid to be sprayed.The remainder of the tube upstream of the section 16 is fabricated froman electrically insulating material. The part of the tube downstream ofthe section 16 may be electrically insulating but preferably thedownstream section will have some means of conducting voltage to theresidual liquid in the downstream section after its trailing surface hascleared the electrode section 16. Thus, the tube section downstream ofsection 16 may be semi-conductive or may have a conductive orsemiconductive track or the like along its inner surface.

In operation, when pressurised fluid is applied to the tube 10 thecolumn 14 is displaced towards the nozzle tip 12 and passes through thesection 16 where it is electrically charged. Prior to reaching thenozzle tip 12, the column 14 is accelerated by the pressurised fluid andconsequently will be moving rapidly by the time the leading face of thecolumn 14 reaches the nozzle tip. In this way, a clean start-up isachieved in the spraying operation since the liquid does not arrive atthe nozzle tip until it has been accelerated. The column 14 on ejectionfrom the tube 10 forms a stable jet 18 which breaks up into electricallycharged particles which disperse as a spray. In the case of liquids,break up of the jet may be primarily hydraulic in nature or it may beinfluenced at least to some extent by the high potential gradientprevailing in the region of the nozzle tip relative to the surroundingsor a target which is to be sprayed. In the latter case, the jet formedby the column as it emerges from the nozzle tip 12 may undergo someelectrostatically induced necking in the manner disclosed in our priorEP-A-510725, the entire disclosure of which is incorporated herein bythis reference.

Once the entire column 14 has been ejected, the pressurised fluidcontinues to discharge from the nozzle tip 12 and serves to purge thetube in readiness for the next operation. The purging action effected bythe pressurised fluid reduces any tendency for stray liquid to remain inthe vicinity of the nozzle tip 12 which could otherwise lead to untidyspray attachment to the nozzle tip at the end of the spraying operationand/or at the beginning of the following spraying operation. The nozzletip 12 is desirably of reduced diameter as shown so that the column is“impact extruded” through the nozzle outlet thereby raising the velocityof the jet 18 further. Such reduction in the diameter of the nozzle tip12 may be achieved by drawing down a tube at one end thereof or bymoulding the tube with a blanked off end and then drilling a smalldiameter hole though the blanked off end by laser drilling or ultrasonicdrilling.

Typically the volume of the column 14 will be substantially constant fora given application and will range from about 2 to 100 microliters, moreusually from 2 to 50 microliters. With appropriate design of the nozzle,particularly the diameter of the outlet at the nozzle tip, materialswith a wide range of volume resistivities can be sprayed successfully.In the case of liquids for instance, we have found that satisfactoryspraying can be achieved with liquids having volume resistivities as lowas 1×10³ ohm cm and even lower (e.g. 2×10² ohm cm) although withresistivities as low as this, the “necking” effect referred to above isnot usually observed. As disclosed in EP-A-510725, electrostaticallyinduced necking is advantageous when very fine droplet sizes arerequired. Where very low resistivity liquids are employed, the absenceof any significant electrostatically induced necking can be compensatedfor, if desired, by the use of a nozzle outlet of small diameter.

Typically the diameter of the outlet at the nozzle tip is no greaterthan 300 micron and usually no less than about 15 micron. For example,the outlet diameter may be in the range from about 20 to about 150micron, more preferably 25 to 125 micron and most preferably 30 to 80micron.

Referring to FIG. 3, the nasal sprayer comprises a housing 30 suitablydimensioned for hand held use. The housing accommodates a high voltagegenerator 32 and a low voltage battery supply 34 for powering thegenerator. The battery supply may comprise one or more replaceablebatteries which may be of the rechargeable type if desired. Thegenerator typically produces a high voltage output from about 1 to 3 kVup to about 12 to 15 kV, preferably from 2 or 3 kV to about 9 to 10 kV.Operation of the generator 32 is controlled by means of a switchactuator 36 suitably positioned for operation by the user while holdingthe device in one hand. In this embodiment, the switch actuator 36 is ofthe pushbutton type and is located generally centrally of the housing 10for ease of operation with the the thumb or other fingers while holdingthe device in the palm of the hand. An earth return path may beestablished through the user for example by providing some form ofcontact on the housing 30, e.g. the switch actuator 36, so that when thedevice is held in the hand, a connection to earth is provided throughthe user.

The housing 30 is fabricated from a plastics material which has goodelectrical insulation properties and is designed in accordance with theteaching of our prior EP-A-441501 in order to allow the use of aninexpensive and compact generator. A nozzle 38 is provided at one end ofthe housing 30 and is located within a nose piece 40 which may be formedwith one or more apertures (not shown) through which air can be drawn bythe user in the course of inhaling through the nose. The nozzle 38 isconveniently fabricated from an electrically insulating, non-wettingplastics material (e.g. PTFE) and communicates with to an axiallyextending passageway 42 which may be in the form of a tube ofelectrically insulating material. In the vicinity of the tip of thenozzle 38, the passageway 42 is provided with an electrode 44 which maybe cylindrical with an inside diameter corresponding generally to theinside diameter of the passageway 42. The electrode 44 is connected tothe high voltage output of the generator 32 via lead 46. The generator32 is energised by operation of the switch actuator 36, part 36A ofwhich is arranged to effect closure of a switch contact 48 by a cammingaction as the actuator 36 is displaced inwardly relative to the housingagainst the action of a spring 49. Closure of contact 48 completes acircuit including the generator 32 and the low voltage source 34,thereby powering the generator. The generator may be of the designdisclosed in EP-A-441501. The spring 49 serves to bias the switchactuator 36 to a position corresponding to deactivation of the generator32.

Liquid from a reservoir 50 is supplied to the passageway 42 via tube 52and one-way valve 54 in response to displacement of plunger 56 connectedby stem 57 to a slidably mounted actuator 58 at the end of the housingremote from the nozzle end. The reservoir 50 may be a replaceable,“plug-in” cartridge. The actuator in this case is operable incrementallyunder the control of a detent 60 mounted in the housing for co-operationwith a ratchet 62 provided internally of the actuator 58 which is in theform of a cap encircling the remote end of the housing. The liquid to bedispensed extends from the reservoir 50 through the tube 52 up to thevalve 54 so that in response to each increment of movement of theactuator 58, a small slug of liquid is transferrred from tube 52 toprime the passageway 42 in the manner illustrated in FIG. 1.

Stepwise actuation of the actuator 58 also serves, through displacementof a plunger 68 mounted on stem 64, to pressurise air in a reservoir 66.The air passes via valve 70 into a pressure chamber 72 which cancommunicate with the passageway 42 under the control of a sliding valve74 carried by the actuator 36. The valve 74 includes a port 76 whichmoves into registry with the passageway 42 when the actuator 36 isoperated. Normally the valve 74 serves to isolate the pressure chamber72 from the passageway 42. However, when the port 76 moves into registrywith the passageway 42 and provides communication with the pressurechamber 72, a pulse of compressed air is injected which serves to ejectthe slug of liquid from the passageway. It will be noted that registryof the port 76 with the passageway 42 is accompanied by energisation ofthe generator and consequently high voltage is applied to the liquidthrough electrode 44 as the liquid travels toward the nozzle tip. At thepoint in time when the high voltage is applied to the liquid, thetrailing surface of the slug will be downstream of the junction betweenthe passage 42 and the passage 52 and hence the slug will be bothphysically and electrically isolated from the liquid in the passage 52and the reservoir 50. Consequently, if the relevant components of thedevice are fabricated from an electrically insulating material, theliquid in reservoir 50 may be at or close to earth potential. Thepassage 80 in the nozzle tip is of reduced cross-section compared withthe passageway 42 for the reasons mentioned in connection withembodiment illustrated in FIG. 1.

In operation, the user initially primes the device and compresses theair by operating the actuator 58, i.e. displacing it in the direction Ain FIG. 3. This results in a slug of liquid being introduced into thepassageway 42 in readiness for the next stage of operation. The userthen registers the nosepiece 40 with the nostril which is to receive thespray and operates the actuator 36 which, during the initial part of itstravel, operates switch 48 to activate the generator 32 and then movesport 76 into registry with passageway 42 allowing release of the airpulse from chamber 72 and consequent ejection of the liquid slug in themanner described with reference to FIG. 2. At the same time as operatingthe actuator 36, the user may inhale through the appropriate nozzle toproduce an air flow through the nosepiece 40 to assist drawing the sprayinto the nasal cavity, although this is not essential to operation ofthe device. Because the spray droplets are electrically charged, theywill rapidly deposit on the lining of the nasal cavity or within theupper respiratory tract thereby ensuring that penetration of the sprayis limited.

Any tendency for deposition of the spray onto parts of the device duringspraying can be reduced by fabricating the nose piece from a goodelectrically insulating material which will tend to hold any charge thatit collects during spraying. Thus, when spraying commences coronaeffects lead to some charge deposition on the nose piece which, in turn,tends to repel the like-charged spray particles.

Referring to FIG. 4, this embodiment is similar to that of FIG. 3 but isconfigured to allow operation of the device by means of a singleoperation on the part of the user. The device comprises a housing 80which is suitably dimensioned for hand held use and accommodates a highvoltage generator 82 and a low voltage battery supply 84 for poweringthe generator. Operation of the generator 82 is controlled by means of aswitch actuator 86 suitably positioned for operation by the user whileholding the device in one hand. An earth return path may be establishedthrough the user for example by providing some form of contact on thehousing 80 so that when the device is held in the hand, a connection toearth is provided through the user.

A nozzle 88 is provided at one end of the housing 80 and is locatedwithin a nose piece 90 which may be formed with one or more apertures(not shown) through which air can be drawn by the user in the course ofinhaling through the nose. The nozzle 88 is conveniently fabricated froman electrically insulating, non-wetting plastics material (e.g. PTFE)and communicates with an axially extending passageway 92 which may be inthe form of a tube of electrically insulating material In the vicinityof the tip of the nozzle 88, the passageway 92 is provided with anelectrode 94 which may be cylindrical with an inside diametercorresponding generally to the inside diameter of the passageway 92. Theterminal passageway 130 provided in the nozzle is of reducedcross-section for the reasons previously discussed. The electrode 94 isconnected to the high voltage output of the generator 82 via lead 96.The generator 82 is energised by operation of the switch actuator 86 viaan arm 150 mounted on a slide 152 after lost motion has been taken up,there being a gap 154 between the forward extremity of the actuator 86and the slide 152. Thus, as the actuator 86 is displaced inwardlyrelative to the housing against the action of a spring 99, the forwardextremity of the actuator 86 contacts slide 152 and displaces it to theleft as viewed in FIG. 4 with consequent operation of the switch 98,activation of the generator 82 and hence application of high voltage tothe electrode 94. Upon release of the actuator 86, the actuator and theslide 152 are restored to the positions shown by springs 99 and 158.

Liquid from a reservoir 100 (not necessarily to scale) is supplied tothe passageway 92 via tube 102 and one-way valve 104 in response todisplacement of plunger 106 connected to the actuator 86 by stem 107 andarm 108. The reservoir 100 may be in the form of a replaceable “plug-in”cartridge. The liquid in reservoir 100 is drawn via one-way valve 110into tube 102 during the return motion of the actuator 86 and isinjected as a slug into the passageway 92 in response to inwarddisplacement of the actuator 86. The lost motion 154 introduces a delaybetween injection of the liquid into the passageway 92 and activation ofthe generator 82.

Inward displacement of the actuator 86 also serves, through displacementof a plunger 114 coupled to the actuator by stem 116 and arm 108, tomaintain a supply of pressurised air in a reservoir 118 by feeding airvia tube 119 and one-way valve 122 to reservoir 118 and associated tube124. Tube 124 can communicate with tube 92 but is normally isolated fromthe latter by slide 152 which acts as a valve. Communication betweentubes 124 and 92 is established when the slide is displaced sufficientlyby the actuator 86 to bring a port 126 into registry with tube 124. Thisis phased in such a way that switch 150 is operated to activategenerator 82 in advance of communication being established between tubes124 and 92. Once communication is established, a pulse of air travelsalong passageway to eject the liquid slug in passageway 92 out of thenozzle 88 in the manner described in relation to FIGS. 1 and 2.

Air is drawn into the device through a filter 130 via valve 132 duringreturn movement of the actuator 86 and hence plunger 114. The reservoir118 may be provided with means for providing a visual indication thatthe reservoir is sufficiently pressurised to initiate dispensingoperations. Initially before the device can be used for dispensingoperations, the cylinder in which plunger 106 operates and theassociated tube 102 must be filled (e.g. as part of the manufacturingprocess).

From the foregoing, it will be seen that the sequence of operations iseffected in response to a single operation of the actuator 86. In thisembodiment, once the device has been initially primed for use, the userwould first register the nosepiece 90 with the appropriate nostril andthen press the actuator 86 inwardly resulting in the following sequence:

operation of plungers 106 and 114 with consequent injection of a liquidslug into tube 92 and pressurisation of the reservoir 118,

activation of the generator to apply high voltage to electrode 94,

transmission of an air pulse along tube 92,

electrical charging of the liquid slug, and

ejection and break up of the slug into a spray.

When the actuator 86 is released for return to the position shown,plungers 106 and 114 and slide valve 152 are all restored to thepositions shown with accompanying replenishment of the liquid and airsupplies in tubes 102 and 119 and deactivation of the generator 82.

In the embodiments described above, a discrete slug of liquid isinjected into the passageway leading to the nozzle. In an alternativeembodiment as illustrated in FIGS. 5 and 6, the arrangement is such thatthe liquid is established as a column within the passageway leading tothe nozzle tip and not necessarily as a slug isolated from the liquidsupply reservoir. Thus, as shown in FIG. 5 (where parts in common withthe embodiment of FIG. 1 are depicted by the same reference numerals),prior to ejection a column 200 of liquid is established within the tube10 which may (although this is not essential) extend withoutinterruption from the main liquid reservoir. The column 200 isestablished in such a way that it extends beyond inlet 202 with itsleading surface 204 retracted from the tip of the nozzle portion 12. Theinlet 202 is connected to a source of pressurised fluid (e.g. air). Whendispensing of the liquid as a spray is initiated, the air is injectedthrough inlet 202 into the tube 10 so as to break into the column ofliquid at that location and thereby isolate part 206 of the liquid whichis then driven past the high voltage electrode 16 and out of the nozzle(see FIG. 6) to form an electrically charged spray of droplets.

What is claimed is:
 1. An electrostatic spraying device for forming aspray from one discreet slug of material, the device comprising anozzle; means for establishing the one discreet slug of said material tobe sprayed within a passage leading to the nozzle outlet such that aleading surface of the one discreet slug is spaced from the nozzleoutlet; means for ejecting the one discreet slug of material from thenozzle; and means for applying high voltage to the one discreet slug ofmaterial so that the spray particles formed by breaking up of thediscreet slug on ejection from the nozzle are electrically charged.
 2. Adevice as claimed in claim 1 in which the ejecting means comprises meansfor pneumatically ejecting said column/slug from the nozzle.
 3. A deviceas claimed in any one of claim 2 in which the high voltage is applied tothe column of material at or near to the nozzle outlet.
 4. A device asclaimed in any one of claims 3 in which the material is liquid; and areduced cross-section portion is provided, leading to the nozzle outlet,the leading surface being located upstream of the reduced cross-sectionportion.
 5. A device as claimed in any one of claim 4 in which thearrangement is such that the jet of material at the point of egress fromthe nozzle has a diameter no greater than 300 micron.
 6. A device asclaimed in any one of claims 5 in which ejection of the column/slug isproduced in response to operation of actuating means by the user.
 7. Adevice as claimed in claim 6 in which operation of the actuating meansis accompanied by priming of the passage leading to the nozzle outletwith the column/slug in preparation for ejection.
 8. A device as claimedin claim 7 in which operation of the actuating means is also accompaniedby operation of a high voltage generator associated with the means forapplying high voltage to the material to be sprayed whereby all of theseoperations together with ejection of the column/slug are effected inresponse to a single operation of the actuating means by The user.
 9. Adevice as claimed in claim 7 in which ejection of the column or slugand/or application of the high voltage thereto are effected in responseto a separate operation of the actuating means or operation of adifferent actuating means which effects priming and/or ejection.
 10. Adevice as claimed in claim 1 in which the tip region of the nozzle is ofreduced diameter relative to that section of the nozzle upstream of thetip region.
 11. A device as claimed in claim 1 in which the high voltageis unipolar.
 12. A device as claimed in any one of claims 11 in whichthe high voltage is bipolar.
 13. A device as claimed in claim 12 inwhich the arrangement is such that successive columns/slugs (orsuccessive groups of columns/slugs) of material discharged from thenozzle are charged with voltage of opposite polarity.
 14. A device asclaimed in claim 1 in which the material is discharged as a jet which,at the point of egress from the nozzle, has a diameter in the range fromabout 20 to about 150 micron.
 15. A device as claimed in claim 14 inwhich the material is discharged as a jet which, at the point of egressfrom the nozzle, has a diameter in the range from 25 to 125 micron. 16.A device as claimed in claim 15 in which the material is discharged as ajet which, at the point of egress from the nozzle, has a diameter in therange from 30 to 80 micron.
 17. A device as claimed in claim 1 in whichthe device additionally includes a reservoir for containing the materialto be sprayed, the passage connecting the reservoir to the nozzle.
 18. Adevice as claimed in claim 17 in which the trailing surface of thecolumn/slug is isolated from the remainder of the material in thereservoir.
 19. A device as claimed in claim 18 in which the trailingsurface of the column/slug is physically isolated from the remainder ofthe material in the reservoir.
 20. A device as claimed in claim 18 inwhich the trailing surface of the column/slug is electrically isolatedfrom the remainder of the material in the reservoir.
 21. A device asclaimed in claim 18 in which the trailing surface of the column/slug isphysically and electrically isolated from the remainder of the materialin the reservoir.
 22. A device as claimed in claim 1 in which thematerial to be sprayed is a liquid having a bulk resistivity of lessthan about 1×10⁷ ohm cm.
 23. A device as claimed in claim 21 in whichthe liquid has a bulk resistivity of less than 1×10⁴ ohm cm.
 24. Adevice as claimed in claim 23 in which the liquid has a bulk resistivityof 1×10³ ohm cm or less.